Certified Rhythm Analysis Technician (CRAT) Practice Exam

A normal sinus rhythm is characterized primarily by a regular rhythm. This means that the heartbeats occur at consistent intervals, reflecting a stable and predictable timing in the firing of the sinoatrial (SA) node, which is the natural pacemaker of the heart. The regularity of the rhythm is a hallmark characteristic that ensures adequate cardiac output and efficient blood circulation throughout the body.

While heart rate is relevant—typically ranging from 60 to 100 beats per minute for normal sinus rhythm—variations within this framework do not necessarily indicate a normal sinus rhythm in all contexts. A heart rate greater than 100 bpm would classify as tachycardia, which is outside the normal definition. The presence of ectopic beats indicates irregular pacing from areas outside the SA node, thus disrupting the normal sinus rhythm. Lastly, a flat baseline is often observed in normal rhythm recordings but does not define the sinus rhythm itself; changes in baseline can indicate various conditions that are not consistent with a stable sinus rhythm.

In summary, the most defining parameter of a normal sinus rhythm is its regular rhythm, which denotes the orderly electrical activity initiated by the SA node and propagated through the heart.